On 1/23/23 11:17, Richard Fitzgerald wrote: > On 23/01/2023 16:38, Pierre-Louis Bossart wrote: >> >> >> On 1/23/23 10:08, Richard Fitzgerald wrote: >>> On 23/01/2023 15:50, Pierre-Louis Bossart wrote: >>>> >>>> >>>> On 1/23/23 08:53, Charles Keepax wrote: >>>>> On Fri, Jan 20, 2023 at 10:20:50AM -0600, Pierre-Louis Bossart wrote: >>>>>> On 1/20/23 03:59, Charles Keepax wrote: >>>>>>> On Thu, Jan 19, 2023 at 11:12:04AM -0600, Pierre-Louis Bossart >>>>>>> wrote: >>>>>>>> There should be an explanation and something checking that both >>>>>>>> are not >>>>>>>> used concurrently. >>>>>>> >>>>>>> I will try to expand the explanation a litte, but I dont see any >>>>>>> reason to block calling both handlers, no ill effects would come >>>>>>> for a driver having both and it is useful if any soundwire >>>>>>> specific steps are needed that arn't on other control buses. >>>>>> >>>>>> I think it's problematic if the peripheral tries to wake-up the >>>>>> manager >>>>>> from clock-stop with both an in-band wake (i.e. drive the data line >>>>>> high) and a separate GPIO-based interrupt. It's asking for trouble >>>>>> IMHO. >>>>>> We spent hours in the MIPI team to make sure there were no races >>>>>> between >>>>>> the manager-initiated restarts and peripheral-initiated restarts, >>>>>> adding >>>>>> a 3rd mechanism in the mix gives me a migraine already. >>>>> >>>>> Apologies but I am struggling see why this has any bearing on >>>>> the case of a device that does both an in-band and out-of-band >>>>> wake. The code we are adding in this patch will only be called in the >>>>> in-band case. handle_nested_irq doesn't do any hardware magic or >>>>> schedule any threads, it just calls a function that was provided >>>>> when the client called request_threaded_irq. The only guarantee >>>>> of atomicity you have on the interrupt_callback is sdw_dev_lock >>>>> and that is being held across both calls after the patch. >>>>> >>>>> Could you be a little more specific on what you mean by this >>>>> represents a 3rd mechanism, to me this isn't a new mechanism just >>>>> an extra callback? Say for example this patch added an >>>>> interrupt_callback_early to sdw_slave_ops that is called just >>>>> before interrupt_callback. >>>> >>>> Well, the main concern is exiting the clock-stop. That is handled by >>>> the >>>> manager and could be done >>>> a) as the result of the framework deciding that something needs to be >>>> done (typically as a result of user/applications starting a stream) >>>> b) by the device with an in-band wake in case of e.g. jack detection or >>>> acoustic events detected >>>> c) same as b) but with a separate out-of-band interrupt. >>>> >>>> I'd like to make sure b) and c) are mutually-exclusive options, and >>>> that >>>> the device will not throw BOTH an in-band wake and an external >>>> interrupt. >>> >>> Why would it be a problem if the device did (b) and (c)? >>> (c) is completely invisible to the SoundWire core and not something >>> that it has to handle. The handler for an out-of-band interrupt must >>> call pm_runtime_get_sync() or pm_runtime_resume_and_get() and that >>> would wake its own driver and the host controller. >> >> The Intel hardware has a power optimization for the clock-stop, which >> leads to different paths to wake the system. The SoundWire IP can deal >> with the data line staying high, but in the optimized mode the wakes are >> signaled as DSP interrupts at a higher level. That's why we added this >> intel_link_process_wakeen_event() function called from >> hda_dsp_interrupt_thread(). >> >> So yes on paper everything would work nicely, but that's asking for >> trouble with races left and right. In other words, unless you have a > > Wake up from a hard INT is simply a runtime_resume of the codec driver. > That is no different from ASoC runtime resuming the driver to perform > some audio activity, or to access a volatile register. An event caused > a runtime-resume - the driver and the host controller must resume. > > The Intel code _must_ be able to safely wakeup from clock-stop if > something runtime-resumes the codec driver. ASoC relies on that, and > pm_runtime would be broken if that doesn't work. Like I said before, the Intel code will work with either b) or c). Using both to exit clock stop is not a recommended/tested solution, and it's not something I have a burning desire to look into. If you register an external IRQ, then pretty please describe your device as not 'wake_capable'. >> very good reason for using two wake-up mechanisms, pick a single one. >> >> (a) and (c) are very similar in that all the exit is handled by >> pm_runtime so I am not worried too much. I do worry about paths that >> were never tested and never planned for.
